News | Published:

Societies and Academies

    Naturevolume 115pages821823 (1925) | Download Citation

    Subjects

    Abstract

    LONDON. Royal Society, May 14.—E. C. C. Baly and Elizabeth Semmens: The selective photochemical action of polarised light. I. The hydrolysis of starch. Starch grains in weak enzyme solution are hydrolysed under the influence of polarised light, whilst very little or no action takes place in ordinary light of the same intensity. In the case of potato and maize starch diastase was used, whilst in the case of wheat starch the natural enzyme sufficed. The slides were placed on microscope stages and illuminated from below so that the progress of the hydrolysis could be watched. Both daylight and artificial light were used with equal success.—R. B. Thomson and H. B. Sifton: Resin canals in the spruce (Picea). An anatomical and cecological study and its bearings on phylogeny. Anastomosis between different systems of resin-canals is rare in Picea. The bast has only horizontal canals, with bulbous expansions. Horizontal canals are strictly confined to the secondary rays. The canals, except in the wood, show cambial growth in size and thickness of wall. Formation of canals is not dependent on increased vigour or food-supply, and in secondary tissues it is always connected with injury or irritation of the cambium. The root, being very subject to injury, has a well-developed system of canals. In primary wood of the root the appear ance of canals is preceded by that of solid strands of cellular tissue. Accumulation of repeated wound-stimuli explains the sporadic occurrence of canals in twigs of trees of species from which canals are otherwise absent. The whole evidence favours the hypothesis of a phylogenetic increase of sensitiveness to wound-stimuli among Coniferse.-H. G. Cannon: On the segmental excretory organs of certain fresh water ostracods. The "shell gland "of the fresh water ostracods, which has previously been described as the antennal gland, is of unknown function, but is in no way serially homologous with the true segmental excretory organs. These occur in both antennal and maxillary segments. The antennal gland (hitherto undescribed) consists of an end-sac with an intraceliular duct leading to the exterior, consisting of three cells only. It attains its maximum development in the fourth larval stage, after which it loses connexion with the exterior and degenerates. The maxillary gland consists of an end-sac with an efferent intraceliular duct consisting of four cells only. Its end-sac is a true ccelomic sac. Its duct is formed by an ingrowth of ectodermal cells, that finally become overgrown by the surrounding ectoderm. The development of the "shell gland "has been partly described. The part previously considered as a typical end-sac, and therefore of mesodermal origin, arises from a group of ectodermal cells in outer layer of shell-fold.-E. G. T. Liddell and J. F. Fulton: Observations on ipsilateral contraction and "inhibitory "rhythm. Simultaneous mechanical and electrical records have been obtained (with string galvanometer and torsion-wire myograph of high frequency) of responses of quadriceps extensor muscle (cat) to various forms of reflex stimulation, before and shortly after section of the posterior root supply of the muscle. When the normal muscle is renexly stimulated at 50 per sec. through the sciatic nerve of the same side, a small rapidly developed con traction ("ipsilateral ") results, in which the rhythm of stimulus may be seen in both string and myograph. Crossed stimulation at 15 to 20 sec. before cutting the posterior roots also produces a response, but later, the rhythm tends to be obliterated through the appearance of increasingly large numbers of "second ary "waves. After cutting, the secondary waves are more numerous from the start. Increase in mechanical tension increases amplitude of both primary and secondary waves. A single moderately strong break-shock inhibition during a crossed extension response causes, through suppression of secondary waves (repetitive asynchronous after-discharge), an enhancement of primary excitatory rhythm in both string and myograph. Repetitive inhibition, if weak, produces the same effect; if strong, it gives rise to a rhythm of its own rate in both records. This "inhibitory"rhythm during "complete "inhibition seems to be due to the small uninhibitable increment of ipsilateral contraction.- K. Furusawa: Muscular exercise, lactic acid, and the supply and utilisation of oxygen. Pt. X. The oxygen intake during exercise while breathing mixtures rich in oxygen. As was shown before, the maximum oxygen intake may be increased 50 per cent, by the breathing of a mixture rich in oxygen. This can be attributed only to an increased circulation rate of the blood.-J. S. Yeates: The nucleolus of Tmesipteris Tannensis Bernh. In Tmesipteris the maximum number of nucleoli in resting cells of the sporophyte is six. These are formed at telophase by aggregation of small bodies and are often visibly continuous with telophase chromosomes. In sister-telophase nuclei they frequently correspond in number, in size, and in position. During prophase and metaphase the nucleoli are connected with the ends of chromosomes, from which they finally become detached and pass ir regularly towards the poles of the spindle. In some cases the full number of these nucleoli remains visible in the cytoplasm when a new generation of nucleoli has arisen in the daughter nuclei. In resting cells of the gametophyte the maximum number of nucleoli is three. The nucleolus is not an independent, self-perpetuating body, but seems to owe its origin to the chromosomes, and arises de novo in each cell-generation.

    About this article

    Publication history

    Issue Date

    DOI

    https://doi.org/10.1038/115821b0

    Comments

    By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

    Newsletter Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing